Re: Performance degradation in commit ac1d794

On Tue, May 31, 2016 at 10:23 PM, Tom Lane <tgl@sss.pgh.pa.us> wrote:
> Noah Misch <noah@leadboat.com> writes:
>> On Tue, May 31, 2016 at 10:09:05PM -0400, Robert Haas wrote:
>>> What I *think* is going on here is:
>>> - ac1d794 lowered performance
>>> - backend_flush_after with a non-zero default lowered performance with
>>> a vengeance
>>> - 98a64d0 repaired the damage done by ac1d794, or much of it, but
>>> Mithun couldn't see it in his benchmarks because backend_flush_after>0
>>> is so bad
>
>> Ashutosh Sharma's measurements do bolster that conclusion.
>
>>> That could be wrong, but I haven't seen any evidence that it's wrong.
>>> So I'm inclined to say we should just move this open item back to the
>>> CLOSE_WAIT list (adding a link to this email to explain why we did
>>> so).  Does that work for you?
>
>> That works for me.
>
> Can we make a note to re-examine this after the backend_flush_after
> business is resolved?  Or at least get Mithun to redo his benchmarks
> with backend_flush_after set to zero?

Ashutosh Sharma already did pretty much that test in the email to
which I linked.

(Ashutosh Sharma and Mithun CY work in the same office and have access
to the same hardware.)

-- 
Robert Haas
EnterpriseDB: http://www.enterprisedb.com
The Enterprise PostgreSQL Company